Air Injection: Description and Operation

Typical A.I.R. System:

SYSTEM DESCRIPTION

This system is used to reduce Carbon Monoxide (CO), Hydrocarbon (HC) and Nitrous Oxide (NO,) emissions. It also heats up the catalytic converter quickly on engine start-up so conversion of exhaust gases will start quickly.

A dual bed converter is used. It consists of a three way catalyst (which controls all three emissions) in series with a two way catalyst (which controls only HC and CO). Both are in one housing. A pipe between the two converters allows air to be injected into the two way converter to increase its efficiency to further control HC and CO.



The A.I.R. system includes:

^ An Air Pump:
A belt driven pump on the front of the engine and supplies the air to the system. Intake air passes through a centrifugal filter fan at the front of the pump, where foreign materials are separated from the air by centrifugal force.
^ A Control Valve:
Air flows from the pump through an ECM controlled valve (called a control valve) through check valves to either the exhaust ports or the converter.
^ Check Valves:
The check valves prevent back flow of exhaust into the pump in the event of an exhaust backfire or pump drive belt failure.
^ Necessary plumbing.

Electrical Air Switching and Electrical Divert (EAS EDV) Valves:

CONTROL VALVE DESCRIPTION

ELECTRIC AIR SWITCHING or ELECTRIC DIVERT VALVE (EAS/EDV)

The system uses vacuum operated ECM controlled valves which combine both the divert function and the A.I.R. switching function as two valves in series. These are the electric divert valve and the electric air switching valve.


^ The air control (divert) valve provides air divert to the air cleaner for converter protection or directs air to the switching valve.
^ The air switching valve directs air to the exhaust ports during cold engine operation or anytime the fuel control system is in "Open Loop" and between converter beds during warm engine operation and the system is in "Closed Loop."
^ When divert is needed, the ECM turns "OFF" the solenoid in the air control section of the valve, causing air to be diverted to the air cleaner or atmosphere.
^ Divert occurs under the following conditions:
^ Rich operating condition.
^ When the ECM recognizes a problem and sets the "Service Engine Soon" light.
^ During deceleration, very high vacuum.
^ High rpm when air pressure exceeds the setting for relief valve in the air control valve.


RESULTS OF INCORRECT OPERATION

If no air (oxygen) flow enters the exhaust stream at the exhaust ports, or the converter pipe, HC and CO emission levels will be too high.

Air flowing to the exhaust ports at all times could cause a rich ECM command and increased temperature of the converter.

Electrical failure (open circuit) of the control valve will divert air flow to the air cleaner at all times. Air will flow to the converter at all times if an open circuit occurs to the switching valve (converter solenoid). Mechanical failures in the valves could cause the air to flow incorrectly to the exhaust ports or the converter.